This invention relates to an improvement in apparatus for detecting the presence of oxygen in an anaerobic environment, such as an anaerobic chamber.
A typical use for an anaerobic chamber is in the culturing of strict anaerobes. Various apparatus and pieces of equipment are contained within the enclosure for use in anaerobe culture. The enclosure is typically transparent, clear vinyl plastic for example, and work gloves for use by attending personnel are mounted in the wall of the enclosure. The personnel perform various work tasks within the enclosure via use of the flexible work gloves. The atmosphere within the enclosure is controlled by certain associated equipment and supply gases. Physical access to and from the interior of the enclosure is provided by an entry lock mechanism.
The presence of oxygen, even in minute amounts, can be disruptive to the anaerobic culturing process. Accordingly, anaerobic chambers may include catalyst boxes containing catalysts which are effective to aid in removal of stray oxygen from the chamber atmosphere.
As an aid to the use of an anaerobic chamber it is desirable to have an indicator of the presence of oxygen even though provisions exist for its removal. Because minute amounts of oxygen can potentially have undesired effects on anaerobic culture, it is important to be able to detect trace amounts of oxygen in an anaerobic chamber. While there are a number of commercially available oxygen detectors many of them do not possess a sufficiently high degree of sensitivity to detect trace levels. Other types of sensors which can detect trace levels are rather expensive.
There are known methods for detection of oxygen including: electrical conductivity; electrochemical cells; heat of reaction; paramagnetic analyzers; and thermomagnetic analyzers. Briefly, the electrical conductivity method involves the use of dissolved oxygen; the electrochemical cell method involves a polargraphic oxygen electrode; the heat of reaction method involves the detection of heat which occurs when oxygen and hydrogen combine and typically involves the use of a catalyst, such as palladium, to promote that action; the paramagnetic analyzer method involves the attraction of oxygen into a magnetic field; and the thermomagnetic analyzer method involves the use of heat and the paramagnetic property of oxygen. There is also a zirconium oxide analyzer which involves the use of oxygen concentration on a hot yttria tube and a measurement of differential voltage across the tube wall with a known concentration of oxygen on the inside of the tube.
The present invention relates to a trace level oxygen sensor for anaerobic environments which utilizes the heat of reaction method for detecting oxygen. It provides a number of significant advantages over other oxygen detectors, particularly for use in anaerobic environments. Several embodiments of the generic invention are disclosed. A specific preferred embodiment of the invention comprises a unique organization and arrangement which lends itself to fabrication at a cost which is a significant savings over other types of detectors for use in detecting trace levels of oxygen in an anaerobic chamber adapted for the culture of strict anaerobes. This preferred embodiment of the invention is compact and lends itself to being disposed in any desired position in the anaerobic environment and then connected by means of electrical wires to associated electronic equipment which provides information in a useful form for indicating when oxygen is present in an amount of a trace level. This preferred embodiment of the invention comprises a unique selection, organization, and arrangement of component parts in a compact assembly which does not require any significant modification of the anaerobic chamber except to provide for the wiring connection of the device to the associated electronic equipment which is typically located exterior of the chamber.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.